A variable compression ratio internal engine wherein mechanical compression ratio in combustion chambers can be varied, is disclosed in the Unexamined Japanese Patent Publication No. 2008-075602. The internal engine disclosed in the Unexamined Japanese Patent Publication No. 2008-075602 generally comprises a cylinder block, a cylinder head mounted on the upper portion of the cylinder block and a crank case mounted on the lower portion of the cylinder block. The cylinder block and the cylinder head are mounted on the crank case to be able to move relative to the crank case. The mechanical compression ratio in the combustion chambers are varied by moving the cylinder block and the cylinder head relative to the crank case.